Earl of Clare was a title of British nobility created three times: once each in the peerages of England, Great Britain, and Ireland.
The title derives from Clare, Suffolk, where a prominent Anglo-Norman family was seated since the Norman Conquest, and from which their English surname sprang from possession of the Honour of Clare. The Norman family who took the name 'de Clare' became associated with the peerage as they held, at differing times, three earldoms (Gloucester, Pembroke, and Hertford).
The death of the young Gilbert de Clare, Earl of Gloucester, at the Battle of Bannockburn (1314) entailed the break-up of the Honour of Clare, as he and his young wife were childless and the lands were distributed among three co-heiresses. His death marked the end of the great de Clare family. The family lands, were worth as much as £6000, (equivalent to £4,080,000 in 2015), second only to those of the Earl of Lancaster among the nobility of the realm.
The lands went into royal wardship while the matter of inheritance was settled. By the entail of 1290, the lands could only be inherited by direct descendants of the late earl's father. The late earl's sisters, Eleanor, Margaret (now widowed after the death of Piers Gaveston) and Elizabeth were by 1317 all married to favourites of Edward II: Hugh Despenser the Younger, Hugh de Audley and Roger d'Amory respectively. The three were granted equal parts of the English possessions, but Despenser received the entire lordship of Glamorgan in Wales, politically the most important of the de Clare lands.